The present invention relates to a vehicle headlamp, and more particularly a headlamp mounted on a vehicle, such as a 4-wheel vehicle.
Many vehicle headlamps are each configured to effect a low-beam irradiation in a light distribution pattern in which a horizontal cut-off line is disposed on an oncoming lane side with respect to the front direction of a lighting device.
In a low beam light distribution pattern Pxe2x80x2 of the left light distribution shown in FIG. 10, for example, a horizontal cut-off line CL1 is disposed on the oncoming lane side (right side), and an oblique cut-off line CL2 slanting upward from the horizontal cut-off line CL1 is disposed on the own lane side (left side), whereby a forward visibility of a driver in his own vehicle is secured on the left-hand traffic vehicle lane, while preventing a glare imparted to the oncoming vehicle""s driver.
In the vehicle headlamp illustrated in the figure, light emanating from the light source 118a of a light source bulb having a light source 118a disposed coaxially with an optical axis Ax1 extending substantially in the back/forth direction, and an inner shade 118c covering the light source 118a over a predetermined angular range so as to block light going downward from the light source 118a, is reflected by a reflector 120, thereby forming the low beam light distribution pattern Pxe2x80x2.
When the vehicle is in running motion of turning, the vehicle body rolls due to centrigugal force. For example, when the vehicle body rolls to the oncoming lane side (right side) as in running motion of left turning as shown in FIG. 11, the right and left lamps (headlamps) 110 also tilt to the oncoming lane side (right side). Accordingly, a low-beam light distribution pattern Pxe2x80x2 formed by the beam emitted from the headlamp 110 tilts to the oncoming lane side (right side) (the low-beam light distribution pattern Pxe2x80x2 before tilted is indicated by a two-dot chain line). At this time, the horizontal cut-off line CL1 slants downward to the right. Accordingly, a visibility of a road surface in front of the vehicle (specifically, a visibility of a shaded area A located near the front part of the horizontal cut-off line CL1) deteriorates.
Accordingly, an object of the present invention is to provide a vehicle headlamp configured to effect a low-beam irradiation in a light distribution pattern in which a horizontal cut-off line is disposed on the oncoming lane side in the front direction of the lighting device, which the headlamp is improved such that even when the vehicle body rolls to the oncoming lane side, a visibility of a road surface in front of the vehicle is sufficiently secured.
To achieve the above object, much ingenuity has been exercised to produce inventive and unique elements constituting the lighting device, with provision of a bulb driving mechanism.
According to the present invention, there is provided a vehicle headlamp configured to effect a low-beam irradiation in a light distribution pattern in which a horizontal cut-off line is disposed on the oncoming lane side in the front direction of a lighting device, the headlamp comprising 1) a light source bulb including a light source disposed coaxially with an optical axis extending substantially in the back/forth direction, and a shade member which covers the light source over a predetermined angular range, 2) a reflector for reflecting the light from the light source to the front, and 3) a translucent cover provided in front of the reflector, wherein a horizontal cut-off line forming area for controlling a light distribution control for forming the horizontal cut-off line is provided on the reflector or the translucent cover, in that at least apart of the horizontal cut-off line forming area is formed with a plurality of reflection elements or lens elements, the reflection elements or the lens elements slant toward the optical axis by an angle of 3xc2x0 to 10xc2x0 from the upper end to the lower end with respect to the vertical direction, and a bulb driving mechanism is provided, and when the headlamp tilts in the horizontal direction, the bulb driving mechanism rotates the light source bulb about the optical axis in an opposite direction to the tilting direction of the headlamp.
The xe2x80x9clight sourcexe2x80x9d is not limited to any specific light source if it is disposed coaxially with an optical axis extending substantially in the back/forth direction. Examples of the light sources are a filament of a halogen lamp or the like, and a discharge light emitting part of a discharge bulb.
The xe2x80x9cshade memberxe2x80x9d is not limited in its construction in particular. For example, it may be an inner shade disposed under the light source, or a light shielding film formed, by coating, on a glass tube of the light source bulb.
The xe2x80x9ca predetermined angular rangexe2x80x9d means an angular range having the central angle of 165xc2x0 between the horizontal direction of the own lane side with respect to the optical axis and a direction slanting, at an angle of 15xc2x0, downward with respect to the horizontal direction of the oncoming lane side, or an angular range having the a central angle of 165xc2x0, of which the middle part is partially removed.